1. Field of the Invention
The invention concerns dynamoelectric machines, specifically motors and generators (including alternators). The invention especially concerns dynamoelectric machines having brushless stator coils and permanent magnet rotors. The invention also concerns a fixture for winding the stator coils.
2. Description of Related Art
Dynamoelectric machines that have a permanent magnet rotor and a brushless stator of one or more ironless coils can be inexpensive, but typically are inefficient. Greater efficiency can be attained by winding the stator on a stack of laminated steel plates, but with loss of economy, because the production of the steel plates requires expensive tooling, and their assembly with insulating sheets can also be expensive. Furthermore, laminated steel plates greatly increase the weight of a motor and involve eddy current losses.
An inexpensive dynamoelectric machine that has a permanent magnet rotor and one or more substantially ironless coils is disclosed in my U.S. Pat. No. 4,883,981. I believe it to be at least as efficient as any equally inexpensive dynamoelectric machine on the market, and more efficient than most. Another inexpensive dynamoelectric machine is disclosed in my U.S. Pat. No. 4,814,654.
In the embodiment of the dynamoelectric machine shown in FIGS. 10, 11 and 14 of my '981 patent, a plastic frame supports a thin-walled stator coil having a large number of circular turns that form a toroid. The legs of the stator coil extend along the truncated spherical working faces of a permanent magnet rotor which is mounted on a metal shaft that is journalled in the frame so that the working faces of the magnet pass close to the legs of the coil. That and other dynamoelectric machines of said patent can be miniaturized for uses where space is at a premium, e.g., as a fan motor or a motor for driving disks or tapes. Unfortunately, miniaturization can result in reduced efficiencies. Furthermore, miniturized coils can be more difficult to wind, hence more expensive.